Doctor blade holder



Sept. 22, 1970 H. E. DUNLAP ET AL 3,529,315

' DOCTOR BLADE HOLDER Filed Jan; 27, 1969 4 Shee't-Sheet 1 INVENTORSHAROLD E. DUNLAP ROGER E. BEDARD Rpsan & SIEINHILPER ATTORNEYS Sept. 22,1970 DUNLAP- ET AL 3,529,315

DOCT OR BLADE HOLDER Filed Jan. 27, 1969 4 Sheets-Sheet 2 INVENTORSHAROLD E. DUNLAP ROGER E. BEDARD Rosin & srzmmuc R ATTORNEYS H. E.DUNLAP ET AL 3,529,315

Sept. 22, 1970 DOCTOR BLADE HOLDER 4 Sheets-Sheet 5 Filed Jan. 27, 1969HAROLD E. DUNLAP ROGER E. BEDARD (nvenfors Afforneys Sept. 22, 1979DUNLAP ET AL 3,529,315

DOCTOR BLADE HOLDER 4 Sheets-Sheet 4.

Filed Jan. 27, 1969 FIG-.7

HAROLD E. DUNLAP ROGER E. BEDARD /nven/0rs 5V Rosm & STEINHILPERAf/omeys United States Patent 3,529,315 DOCTOR BLADE HOLDER Harold E.Dunlap and Roger E. Bedard, Auburn, Mass.,

assignors to Lodding Engineering Corporation, Auburn, Mass., acorporation of Massachusetts Continuation-impart of application Ser. No.719,413,

Apr. 8, 1968. This application Jan. 27, 1969, Ser.

Int. Cl. D21g 3/04 US. Cl. 15-25651 Claims ABSTRACT OF THE DISCLOSURE Anew support and displacement mechanism is provided for a wiper elementsuch as a doctor blade whereby a uniform and self-compensatingpositioning of the element is achieved at all locations along itslength. The blade is pivotally mounted, and correct spacing or positionis provided by a tubular member mounted longitudinally along the rearportion of the blade. The walls of the tubular member are flexible, andlargely inelastic, and the tube is filled to partial capacity with anon-compressible fluid such as a liquid or fluidized particles. Air orother compressible fluid is excluded from the tubular member. A completedoctor blade assembly is described.

This application is a continuation-in-part of copending application Ser.No. 719,413 filed Apr. 8, 1968 and now abandoned.

BACKGROUND OF INVENTION The use of wiper elements such as doctor bladesis well established in numerous arts such as the coating art, the papermaking art, and the like. The doctor blade in these arts is positionedadjacent to a moving surface, and is brought into close proximity or incontact with the surface so as to regulate the thickness of a coatingthereon, or to scrape or remove excess coating, foreign material or thelike from the surface. In the paper making art, for example, a doctor isemployed at various places to remove water from the surface of theroller and to maintain the substantial absence of foreign material onthe surface. The doctor may be employed at any of the rotating rolls ordrums as desired.

It is known that a pivotally mounted doctor blade can be brought to thedesired position of adjustment with relationship to the moving surfacewith a minimum of difiiculty. The adjustment mechanism for the blade maybe a mechanical adjustment such as rotation, retraction, extension orthe like, as desired. Recently, there has been employed a pneumaticadjustment through the use of an inflatable tube positioned against therear surface of the blade, and adjustment is achieved by adjusting thegas pressure in the tube. A pneumatic adjustment has certain obviousadvantages, but it also has certain disadvantages. For example, apneumatic device requires relatively delicate adjustment, and isessentially equivalent to a spring member. While it is possible for theoperator to adjust the air pressure in the tube, this in turn leads tofurther disadvantages if the operator has the opportunity andresponsibility to maintain blade adjustment.

In addition, there are certain limitations in pneumatic adjustments, andfor that matter, in any prior mounting system. In many situations, adoctor blade is required to operate in conjunction with a surface whoseshape at the line of intersection varies with operating conditions orwith the position of the blade element on the work surface. For example,calender rolls frequently operate under relatively high pressure, andare crowned so that there is self-compensating adjustment for thebending of the roller under pressure. This means that the shape of3,529,315 Patented Sept. 22, 1970 a surface segment or line ofintersection with a doctor blade changes from position to positionaround the roller, and also with machine speed, roller pressure and thelike. To some extent, this can be compensated by machining the doctorback or support member for the blade holder and again there arelimitations caused by the varying operating conditions.

DESCRIPTION OF INVENTION According to the present invention, a number ofthe difiiculties and limitations in prior art doctor blade mountings areovercome by positioning a pivotally or rotatably mounted doctor bladeadjacent to the surface to be maintained, and controlling the positionof the opposite portion of the blade by displacement against a yieldablemember comprising a tube having a largely inelastic but yielding wall,filled to a fraction of its maximum capacity with a non-compressiblefluid and excluding compressible material. The invention is illustratedin the following specification, and in the drawings in which:

FIG. 1 is an exploded view of a doctor blade assembly;

FIG. 2 is an end view in cross section of a doctor assembly;

FIG. 3 is an end view of a segment of a support member awaiting asealing operation;

FIG. 4 is a view of a slotted blade according to one embodiment of theinvention;

FIG. 5 is an end view in cross-section of another doctor assembly;

FIG. 5A is a cross-section of a part of the doctor assembly shown inFIG. 5 but taken in another plane parallel to the section of FIG. 5;

FIG. 6 is an isometric view of the support member of FIG. 5;

FIG. 6A is a fragmentary plan view of the support member; and

FIG. 7 illustrates the relationship of the blade and blade-retainershown in FIG. 5.

In FIGS. 1 and 2 is shown one embodiment of a doctor blade assembly,generally designated 10, mounted on a support member 11. The supportmember 11 is suitably positioned on a machine or device utilizing adoctor mechanism for smoothing a coating, removing an excess of materialor the like. Such machine may, for example, be a paper machine and it isunderstood that the doctor blade assembly 10 illustrated in FIGS. 1 and2 is well adapted for the rolls requiring doctoring in a paper machine,and in textile machines and the like.

A frame member 12 of the blade assembly is secured to the support member'11 by conventional means such as a bolt 14. Either the support memberitself, or the positioning of frame member 12 on the support member 11is adjustable, as is conventional, to achieve proper action between thedoctor blade and a work surface. Frame member 12 along its front end hasa jaw 15 characterized by being a smooth edged, extremely flat surfacethus forming a uniform supporting pivot for a doctor blade 16 which isremovably positioned in the blade assembly. A lower jaw 17 is mounted onthe frame member 12, by suitable means. For example, a spacer bar 19 andplate 20 may be secured by rivets 21, holding the lower jaw member 17parallel with frame member 12, with the lip 22 thereof defining anopening or mouth along the length of the blade assembly. As shown inFIG. 2, the mouth defined by upper and lower jaws 15 and 17 is adaptedto receive a removable doctor blade 16 with or without a support plate24.

In the embodiment of the invention illustrated in FIGS. 1 and 2, asupport plate 24 is removably positionable in the jaws 15 and 17, beingrelatively loosely held in the jaws. Desirably, upper jaw 15 is rigiddefining an immovable pivot for blade 16, and lower jaw 17 is relativelyflexible, causing it to press lightly against support plate 24. Thesupport plate 24 is a thin blade-like member, preferably of metal anddesirably of a non-corrosive material such as stainless steel, with anend section or guard 25 bent downward over the edge of the bladeassembly, effectively positioning the assembly in a longitudinaldirection. Dimples 18 in the blade retain it in the assembly.

Positioned along and within the mouth of the blade assembly is aflexible support member 26 held loosely in position by retainers 27, theflexible support member 26 being positioned to support the blade 16behind the pivot position of upper jaw 15, flexibly holding the blade ata desired rotational position within the doctor blade assembly as willbe further described herein. The blade is removably secured in theassembly along the upper surface of support plate 24, the pressures ofjaws 15 and 17 being suflicient to secure blade 16 in position whileallowing it to be removed manually when desired. When blade 16 isremoved, support plate 24 is loosely held by the jaws, and dimples 29are positioned to prevent plate 24 from being removed by gravity or byan accidental bang.

The support member 26 is shown more fully in FIG. 3. This membercomprises an elongated, hollow, flexible body having a lower wall orbase 30, adapted to rest on and be supported by plate 28 (see FIG. 2).An upper Wall 31 preferably has a smoothly rounded or crowned uppersurface and its center is thicker than the edges. The

upper wall is adapted to yieldably support the support plate 24, anddoctor blade 16, or if desired, directly support the doctor blade. Anormally flat slit or central opening 32 runs lengthwise through thesupport member 26, causing it to resemble a partially flatened hollowtube. Along the edges of slit 32 may be located edge holes 33 adapted toreceive plugs 34. The walls of the support member 26 are a flexible anddesirably relatively inelastic material such as plastic or a heavyrubber or the like. In the normal conditions of operation, the member isessentially unstretched, and thus operatively its walls are not subjectto significant stretching forces.

For use and operation, support member 26 is sealed at one end byapplying a suitable cement to its inner surfaces, plugs 34 are insertedinto the edges and the assembly pressed together and, if desired, heatedto cause an end seal. The member is then filled with a suitablenoncompressible fluid, as for example by holding it in a vertical orinclined position and pouring a fluid into its open end. The fluid isinserted in the absence of substantial pressure until the member iscompletely full, to the exclusion of air, with no more than minimalpressure. The inner edges of the orifice are thoroughly cleaned. Cementis then painted inside the open end of the member, another pair of plugs34 inserted, and the end pressed to seal the member in a condition fullof non-compressible fluid.

If the full benefits of the invention are to be enjoyed, it is importantto avoid filling the member 26 to its full capacity under pressuresuflicient to cause substantial elasticity of the walls of the member,because pressure filling can produce a situation in which some of thecharacteristics of a pneumatic pressure member are created.

The non-compressible fluid may be any suitable liquid such as water,oil, glycerine or other conventional hydraulic fluid. If desired, it maybe a flowable solid such as, for example, finely divided solid particleswhich, particularly if substantially spherical in shape, will flowwithin the support member. It is desired that the non-compressible fluidact as a hydraulic fluid, such as a liquid, to transmit force uniformlyalong the length of the member. A solid material possessing the propertyknown as plastic flow may also be used, with or without confining walls,provided hydraulic force is conveyed by such material.

In the doctor blade assembly as illustrated in the drawings, the bladeis supported behind its axis of rotation against a displaceable materialin the form of a tube of yieldable walls partly filled with anon-compressible fluid such as preferably water or other liquid. Asillustrated, the tube lies in a relatively flat position andconfiguration so as to support the rotatably mounted blade firmly andyet yieldably. As is apparent, the pressure against the rear portion ofthe blade is uniform at all positions, and the blade, nonetheless, isheld firmly and yieldably with a relatively small degree of movability.The control of the blade position or rotation is extremely accurate, andthe incompressibility of the supporting fluid prevents gross movement ofthe blade position in response to varying temperatures of operatingconditions, or in response to localized pressure, or displacement at theoperating edge of the doctor blade.

By considering the forces acting on the blade and on the support member,one can see that the blade is able to act as if it consists of a numberof independent segments. For example, if the operating edge of the bladeis raised at one point along its length by non-uniformity of the surfaceagainst which the blade operates, the rear or supported edge of theblade is correspondingly depressed. This action displaces thenon-compressible fluid away from the point of depression and causes theblade at all points to be held against the operating surface by equalforce, thus causing the remaining length of the blade to be urged torotate against a localized force. In this manner, the blade mounting isautomatically selfcompensating. If the blade is operated against acrowned surface, the act of elevating the central portion of the doctorblade automatically depresses the ends. This permits the blade to haveadded compatability with curved surfaces or with surfaces of changingconfiguration. It also permits the blade to adjust to localized foreignmaterial on the surface Without producing equal adjustment along theentire length of the blade.

In FIG. 4-, is illustrated one embodiment of a slotted blade suitablefor certain applications and uses of doctor blades and adapted tomaximize the flexibility and control imparted to blade assemblies by thedisplacement mounting as disclosed herein. For many uses and operationsof this invention, the doctor blade 16 is a flat sheet of metal,plastic, laminated material or the like, generally rectangular in shapeand having a straight operating edge. It should be relatively flexibleto permit operation without jamming and should be constructed orselected according to the usual skill in the art. However, in someinstances, the embodiment of FIG. 4 is preferred. According to thisembodiment, the rear or supporting portion 36 of the blade member 16 isslotted or divided into segments so that the independent action of theblade is increased. The front or operating edge 37 of the blade isuniform to conform with the work surface. Terminal holes 38 at the endof each slot 39 increase the flexibility of segments 40 and preventslots 39 from tearing during operation or handling. The blade hasincreased ability to turn or bend as pressures are applied against itsoperating edge. The resistance of the blade to a twisting action ishighly dependent on the width of the blade member, and the slottedstructure simulates a narrower blade while permitting the same controland support as is achieved with a Wide blade. As is apparent, one bladesegment can be depressed into the area of the support tube with aminimum of distorting force being carried through the adjacent segments.At the same time, however, the depression of one or several segmentsinto the supporting tube creates its self-compensating displacement ofthe non-compress ible fluid, and the consequent adjustment in theopposite direction to the remaining segments.

The liquid or non-compressible fluid should be chosen so that it is safeand is compatible with the conditions of operation. It should benon-reactive with the material of the walls of the tube. It shouldneither boil nor freeze at operating temperatures, and should have amoderate thermal expansion coeflicient. It should have a relatively highflash point, and should be non-toxic.

The blade assembly, support mechanism and other features of theinvention are useful and applicable in virtually any place where asurface is to be wiped, cleaned, scraped, doctored or the like. Thisincludes the paper making and textile arts, and also includes other usesthat applications as are apparent from the description of the invention.

FIG. 5 shows another embodiment of the invention. Parts which are thesame in FIGS. 2 and 5 have the same reference character. Parts in FIG. 5which have the same function as parts in FIG. 2, but are diflerent instructure, have the same reference character primed. Thus, the upper jawis the same in both, but the lower jaw 17' in FIG. 5 is made integralwith the support member 26, which incorporates several other parts thatare separate in FIG. 2, as appears in FIG. 6. The lower wall 30" of thesupport member extends to one side of the opening 32 to become the lowerjaw 17 and lip 22' of the assembly, and a retainer rib 40' is formedintegrally within the lip 22 for engaging the dimples 29' (which aremore pronounced than dimples 29 in FIG. 2) to hold plate 24 againstaccidental removal. The lower wall 30" extends also to the other side ofthe opening 32 to provide a locking rib 41 for engagement between plateand spacer bar 19 which is notched at 42 (FIG. 5A) to engage the rib 41.The edge along which the locking rib runs is cut out at selectedlocations 42, 43, etc. corresponding to locations of the rivets 21, asshown in FIG. 6A and 5. FIG. 5A is a section taken on a plane betweenthe rivets, for example.

The support member 26' may be made of the same material as member 26.The upper wall 31 is flat, rather than crowned, to provide a largersurface bearing on the underside of the blade 16, if desired. Thethinnest sections of the walls around the opening 32 are at theshoulders 44, 45 at each lower edge of the upper wall 31'. For sealingpurposes, the ends of the support member 26 can be trimmed so that atube having walls uniformly of this thickness extends beyond each end ofthe support member 26', and these ends can be sealed with a suitablecement and/or mechanically clamped shut, if desired. The thickersections will be relatively stiffer, and in particular the jaw 17 can bemade thick enough beyond plate 20 to be as firm and flexible as jaw 17in FIG. 2.

FIGS. 5 and 7 show another structure for retaining blades in theassembly. The upper jaw 15 is fitted with a blade-locking strip 51,which is attached as by rivets 52 to the jaw near but within the lipedge of the jaw and bent on a line 53 parallel to the lip so that thestrip projects from the jaw toward the upper rear surface of the blade,and the rear edge 54 of the strip can bear on the blade. Notches 55 maybe provided in this rear edge, for a purpose to be described.

Blade-retainer clips 61 are fitted to the upper surface of the blade 16,near its rear edge as better shown in FIG. 7. These clips may be made offlat stock, bent over to provide a hook to engage the locking strip 51,and they may be riveted or otherwise attached to the blade 16. When madein the form shown, the notches 55 enable the blade to be inserted andremoved through the lips of the jaws when the clips and notches arealigned as shown in FIG. 7. The blade is locked by moving it length-wiseof the jaws, to engage the clips over the edge 54 of the locking strip,for which purpose a tool may be engaged in the hole 62 at the end of theblade. The blade may be inserted and removed endwise, in which case thenotches 55 will not be required. The clips 61 are exemplary only; otherforms of retainers, such as studs cemented welded or riveted to theblade, may be used.

We claim:

1. A doctor blade assembly comprising a frame membet adapted to bepositioned adjacent a work surface, a rotatably mounted doctor blademounted to be supported by said frame member and pivoted around an axisalong its length, yieldable displacement means positioned to limitrotation of said blade and consequently adapted to retain said blade inoperating position against an adjacent work surface, said yieldabledisplacement means comprising a tubular member having at least oneflexible wall positioned to bear against said blade and containing afixed volume of non-compressible fluid to the exclusion of compressiblematerial, the material of said wall being relatively inelastic such thatin the range of normal conditions of operation it is substantiallyunstretched, whereby substantially uniform force is brought to bearagainst said blade element along its length.

2. An assembly according to claim 1 in which said frame member includesa first jaw member having an edge on which said blade bears at one sidealong said axis, a second jaw member flexibly bearing on the other sideof said blade in a line further removed from said tubular member thansaid axis, and spacer means holding said jaw members apart on said framemember.

3. An assembly according to claim 2 in which said tubular member isincorporated with a base part integrally including means to attach saidbase part to said spacer means and an extension forming said second jawmember.

4. In an assembly for holding a blade element against a work surface, anelongated yieldable blade element supported in said assembly to bearagainst said work surface, yieldable displacement means supported insaid assembly to receive through said blade element reaction pressurefrom said work surface, said yieldable displacement means comprising atubular member disjoined parallel to said blade element and having atleast one flexible wall positioned to bear against said pressure andcontaining a fixed volume of non-compressible fluid to the substantialexclusion of compressible material, the material of said wall beingrelatively inelastic such that in the range of normal conditions ofoperation it is substantially unstretched, whereby substantially uniformforce is brought to bear against said blade element along its length.

5. A blade holder adapted to position a blade to bear against a worksurface with substantially uniform pressure along its entire lengthcomprising:

a blade member shaped to conform with a work surface; and

yieldable displacement means positioned and adapted to bear uniformlyagainst said blade, said yieldable displacement means comprising atubular member having at least one flexible wall positioned to bearagainst said blade and containing a fixed volume of non-compressiblefluid to the substantial exclusion of compressible material, thematerial of said wall being relatively inelastic such that in the rangeof normal conditions of operation it is substantially unstretched.

6. The assembly according to claim 5 wherein the noncompressible fluidis aliquid.

7. A yieldable displacement member adapted for a blade assembly,comprising a tubular member having a base wall adapted to be positionedon a support surface capable of undergoing motion relative to a worksurface, at least one flexible wall adapted to be positioned to bearagainst a blade member, said tubular member being sealed and filled withfixed volume of non-compressible fluid to the exclusion of compressiblematerial, the material of said wall being relatively inelastic such thatin the range of normal conditions of operation it is substantiallyunstretched.

8. A yieldable displacement member for a doctor blade assembly includinga doctor blade and a support member therefor, said displacement membercomprising:

a longitudinally hollow tubular member having a base wall adapted to bepositioned on said support mem- 7 8 ber and to be supported along itslength by said supto said first-named part for attachment to saidsupport port member; and, member. at least one flexible wall adapted tobe positioned to References Cited bear against said doctor blade, saiddisplacement UNITED STATES PATENTS member bein sealed and substantiallyfilled with a fixed volume of liquid to the exclusion of air, the 51566358 12/1925 Whlte' material of said tubular member being relativelyin 2,914,788 12/ 195 9 Smith et elastic such that in the range of normalconditions of operation it is substantially unstretched. LAVERNE DGEIGER Pnmary Exammer 9. A displacement member according to claim 8 hav-10 R. I. SMITH, Assistant Examiner ing a part which extends from saidbase wall to provide an additional support member for a doctor blade.1 1. X.R-

10. A displacement member according to claim 9 hav- 118-125 ing anotherpart extending from said base Wall opposite

